Thermometer



Patented Apr. 30, 1935 PATENT OFFICE 'rnsmuomrrsa Charles E. Githler,comin N. Y., assignor to Corning Glass Works poration of New YorkCorning, N. Y., a cor- Application January 3, 1933, Serial No. 649,985"

1 Claim. (Cl. 73-52) This invention relates to measuring instruments andtubing therefor and more particularly to thermometers and the tubingfrom which they are fabricated.

Thermometers such as are employed in industry and science andparticularly clinical thermometers used in the medical profession arenotoriously hard to read. By that I mean that it is very difficult foran unskilled person or one who is of such instruments.

called upon at only infrequent intervals to take such readings toaccurately determine the position of the mercury column on the scale.This is due to the failure of the bright reflective surface of themercury which is usually employed as the thermally responsive substanceto contrast with the smooth polished surfaces of the glass tubing fromwhich the instruments are usually made.

The object of. the present invention is to facilitate the reading ofmeasuring instruments such as thermometers.

Another object is to simplify the manufacture The above and otherobjects may be attained by employing my invention which embodies amongits features drawing clear glass tubing of the desired cross-sectionwith a relatively large bore, inserting a rod of contrasting glass inthe bore and centering the rod in the bore so as to form a space betweenthe rod and the wall of the bore to accommodate the column of indicatingfluid.

In the drawing:

Fig. 1 is a front view in elevation of a thermometer constructed 'inaccordance with my invention;'

Fig. 2 is a horizontal sectional view on an enlarged scale taken on theline 22 of Fig. 1;

Fig. 3 is an enlarged fragmentary view of Fig. l, the bulb and a portionof the stem being shown in section to more clearly illustrate thedetails of construction; and

Fig. 4 is a view similar to Fig. 2 showing the tubing before the rod ofcontrasting glass has been inserted therein.

Referring to the drawing in detail, the thermometer designated generallyl comprises a length of tubing H which is of substantially triangularcross-section and is formed with the.

usual lens front H2, at the focus'of which is a relatively large borel3. The tube ll is'provided at its lowermost end with the usual bulb Min which expansible fluid such as mercury is contained.v Let into thebore I 3 from its upper end and resting on a reduced portion I5 of thebore which is formed at the joint between the tube I l and the bulb I4is a rod l'l which is formed of glass, the color of which contrasts withthat from which the tube I I is made. In the present illustration therod I1 is shown as being formed of red glass. The rod I] is formed atits lower end with one or more transverse slots or notches IS in orderto allow the mercury l5 to pass from the bulb M into the tube H and fillthe space I9 formed between the wall ofthe bore l3 and the rod IT. Therod Il issupported at its upper end by softening the glass at the upperend of the tube H and sealing the two glasses together as shown in Fig.3. This also seals ofi the upper end of the bore as is commonly done inthe manufacture of thermometers. By thus supporting the rod H atopposite ends in the bore l3 it becomes evident that a space I9 isformed around the rod which receives the mercury when it expands in thebulb I4. Due to the relatively large size of the bore, thermometertubing of this type can be readily drawn and its manufacture isconsiderably simplified as the bore may be pressed in the blank withcomparative ease whereas in the manufacture of thermometer tubing in theusual way great care must be exercised in order to ob-' tain a bore ofthe exact size and shape desired. Inasmuch as I propose to reduce thevolumetric content of the bore by using the rod ll, it becomes evidentthat the manufacture of such tubing is greatly simplified as I need onlyto select a rod which will reduce the space IE! to the desired size.

In operation, the mercury rising in the space l9 which surrounds the rodwill effectively cut oil the view of the rod ll below the upper end ofthe mercury column and consequently no color will appear below themercury level, thus producing a sharply defined line at the mercurylevel which can be readily seen. By this means the height of the mercurywithin the instrument is rendered easily readable against the scalewhich may be engraved on the tube H. Hence it becomes evident that thetemperature may be easily and quickly determined even by a mostinexperienced person.

While in the foregoing there has been shown and described the preferredembodiment of my invention, it is to be understood that minor changes inthe details of construction, combination and arrangement of parts may beresorted to without departing from the spirit and scope of the inventionas claimed.

What I claim is:

A thermometer which includes a. transparent tube having 'a relativelylarge bore, a bulb at one end of t e tube, there being a reduced portionat

